Biological,physical and chemical changes in stored wheat

Six lots of wheat from six farmers' bins in Manitoba were adjusted to a range of 5 moisture contents, held at 6 temperatures and sampled at 6 times during storage. After sampling, seeds were surface sterilized with mercuric chloride and subsamples plated on Czapek's agar, on filter paper moistened with water, or on filter paper moistened with a 7.5% sodium chloride solution. The microflora on the seed was determined, germination counts were made, and the seed was examined by government inspectors for its condition and grade. A total of 1192 samples were examined. In addition, 180 samples were subjected to a fat acidity test. Deterioration for each combination of temperature and moisture, the fungi involved, and the consequent effect on condition, grade and fatty acid content were observed. The effect of high moisture content (>20%) and low temperatures (3–10 ° C) on infection of seed by Penicillium and the consequent effect on germination, condition, grade and fatty acid value are stressed. The interrelationship among fungi, and among fungi and temperature, moisture, storage time, fat acidity values and germination are indicated by correlation coefficient matrices.Deceased July 25, 1982.     

Biological and physical factors influencing the successful engraftment of a cultured human skin substitute

Skin tissue may be engineered in a variety of ways. Our cultured skin substitute (Graftskin, living skin equivalent or G-LSE), Apligraftrade mark, is an organotypic culture of skin, containing both a "dermis" and "epidermis." The epidermis is an important functional component of skin, responsible for biologic wound closure. The epidermis possesses a stratum corneum which develops with time in culture. The stratum corneum provides barrier function properties and gives the LSE improved strength and handling characteristics. Clinical experience indicated that the stratum corneum might play an important role in improving the clinical utility of the LSE. Handling and physical characteristics improved with time in culture. We examined the LSE at different stages of epidermal maturation for barrier function and ability to persist as a graft. LSE grafted onto athymic mice before significant development of barrier function did not withstand bandage removal at 7 days postgraft. LSE grafted after barrier function had been established in vitro were able to withstand bandage removal at day 7. Corneum lipid composition and structure are critical components for barrier function. Media modifications were used in an attempt to improve the fatty acid composition of the stratum corneum. The barrier developed more rapidly and was improved in a serum-free, lipid-supplemented condition. Lipid lamellar structure was improved with 10% of the stratum corneum exhibiting broad-narrow-broad lipid lamellar arrangements similar to human skin. Fatty acid metabolism was not appreciably altered. Barrier function in vitro was 4- to 10-fold more permeable than human skin. Epidermal differentiation does not compromise engraftment or the wound healing ability of the epidermis. The stratum corneum provides features beneficial for engraftment and clinical use. (c) 1996 John Wiley & Sons, Inc.     

Cryptococcus neoformans capsular polysaccharide and exopolysaccharide fractions manifest physical, chemical, and antigenic differences

The human pathogenic fungus Cryptococcus neoformans has a large polysaccharide (PS) capsule and releases copious amounts of PS into cultures and infected tissues. The capsular PS is a major virulence factor that can elicit protective antibody responses. PS recovered from culture supernatants has historically provided an ample and convenient source of material for structural and immunological studies. Two major assumptions in such studies are that the structural features of the exopolysaccharide material faithfully mirror those of capsular PS and that the isolation methods do not change PS properties. However, a comparison of exopolysaccharide made by two isolation techniques with capsular PS stripped from cells with gamma radiation or dimethyl sulfoxide revealed significant differences in glycosyl composition, mass, size, charge, viscosity, circular-dichroism spectra, and reactivity with monoclonal antibodies. Our results strongly suggest that exopolysaccharides and capsular PS are structurally different. A noteworthy finding was that PS made by cetyltrimethylammonium bromide precipitation had a larger mass and a different conformation than PS isolated by concentration and filtration, suggesting that the method most commonly used to purify glucuronoxylomannan alters the PS. Hence, the method used to isolate PS can significantly influence the structural and antigenic properties of the product. Our findings have important implications for current views of the relationship between capsular PS and exopolysaccharides, for the generation of PS preparations suitable for immunological studies, and for the formulation of PS-based vaccines for the prevention of cryptococcosis.     

The seasonal factors influencing child malnutrition on the Nembi Plateau,Papua New Guinea

A sample of children from the Nembi Plateau, Papua New Guinea, is monitored for nutritional status, episodes of sickness and disease, diets, work activity of mothers, and weight changes; and health and census records are examined for seasonal patterns of disease, deaths, birth, and birth weights. A seasonal pattern in birth weight reinforced by a seasonal pattern in growth performance and compounded by a seasonal pattern of disease suggests that the time of year in which a child is born is important to the child's growth and health. Yields, labor, and ritual surrounding the gardens give rise to the seasonal pattern of events that impinge upon the health of children.     

泰国蒙河流域水沙变化趋势及影响因素

水沙变化是影响泰国社会经济发展的重要因素。基于湄公河支流蒙河流域下游乌汶水文站1980—2014年径流量和输沙量监测数据,运用线性回归、Mann-Kendall及小波变化等方法分析了水沙序列的演变规律,探讨了流域水沙变化的驱动力。结果表明: 研究期间,蒙河流域年径流量呈微弱增加趋势,输沙量呈减少趋势;2000年以前,输沙量与径流量保持同步变化,但2000年以来输沙量显著减少;汛期径流量和输沙量均呈下降趋势。水沙突变点的发生年份不完全一致,径流量的突变点分别发生在1999、2006和2011年,而输沙量的突变点为1986、1999和2011年。径流量变化的主周期依次为14、8和4年,输沙量的主周期依次为32、12、9及4年,除输沙量32年变化周期外,水沙变化周期基本一致,均与南方涛动、地极移动、太阳黑子活动等因素有关。月径流量与输沙量具有显著的相关关系。海-气作用和人类活动是流域水沙变化的重要影响因素。厄尔尼诺和拉尼娜与流域降雨关系密切,并直接影响流域水沙变化。2000年以来,流域内建设用地面积增加,林地面积减少,流域产流能力提高,而水库大坝的建设导致流域汛期径流量和输沙量减少,抵消了林地减少对输沙量增加的影响。     

Ecological factors influencing the evolution of insects' chemical defenses

How insect defense chemicals have evolved has remained relativelyunderstudied, compared with the evolution of aposematic signalsof such defenses. Because there is mounting evidence that chemicaldefenses can generally be expected to be costly, understandingthe evolution of such defenses and their maintenance in theface of the potential for automimicry (signaling by individualsthat do not invest in defense) is nontrivial. One potentialexplanation is that chemically defended insects suffer lessfrom predation than those that do not invest in chemical defenses.Here, we use a series of models to explore aspects of the evolutionof such costly chemical defenses. Our models predict that investmentin costly defenses can occur across a wide range of predationintensities; however, if predation intensity is low, then thedefense has to be very effective to be selected, unless thedefense is very cheap. Furthermore, the evolution of antipredatorydefenses will be relatively insensitive to the severity of anymechanism, whereby prey pay a cost every time they use theirdefense against an attacking predator even if they survive theattack, but sensitive to the form of the relationship betweeninitial investment in constituting the defense and survivalbenefit. Once defense becomes common in the prey population,prey may get a frequency-dependent benefit if predators learnto avoid prey of this type after several attacks. Finally, wepredict that increasing the rate of avoidance learning by predatorsencourages reduced investment in antipredatory defenses by prey.The potential for these predictions to be tested empiricallyis discussed.     

Combined effect of some physical and chemical factors

The effect of simultaneous exposure to noise and dimethylformamide (DMF), noise and xylol and also vibration and lead on the metabolism of the myocardium of albino rats was studied. Combined effect of the factors was examined by the method of bifactorial design of the experiment. The animals were exposed to noise, intensity 46, 85 and 95 dB (2 and 4 hours), DMF in doses of 0.25, 1.00 and 5.00 ml . kg-1 (5 days in a week), and xylol in a concentration of 300 mg . m-3 (4 hours, 5 days in a week) for a period of 1.5 months, as also to vibration, intensity 100 Hz, 4 m . sec-2 (2 hours) and lead acetate in a dose of 20 mg . kg-1 (daily for a period of 10 days). The activity of GlDG, SucDG, LDG, G6PDG, G6P-ase, PGM and CytO in the myocardium of experimental and control animals was examined. Disturbances in metabolic and energy processes in the heart muscle were established after both isolated and combined exposure to the effect of the factors. Results of bifactorial variance analysis demonstrate that combined effect of noise and DMF results in not only independent effect of the two factors, but also in their interaction. Isolated effect of two factors (vibration and lead) can be assessed according to the relationship of some enzymes; their interaction can be noticed in GlDG, ATP-ase and G6P-ase.(ABSTRACT TRUNCATED AT 250 WORDS)     

坝地剖面泥沙有机碳分解特征及其影响因素

黄土高原地区已建成的5.6万余座淤地坝累计拦截有机碳0.95 Pg,是陆地生态系统重要的碳汇,但是目前对其分解机制仍知之甚少,难以量化其在陆地碳循环中的作用。本研究通过模拟原始沉积条件下的泥沙环境(缺氧条件)进行矿化培养,并比较假定泥沙暴露在有氧情况下的有机碳分解速率,探究有机碳分解速率的影响因素。结果表明: 坝地泥沙在原始沉积条件和暴露在有氧条件下有机碳分解速率均值分别为(6.47±4.06)和(56.66±17.78) mg C·kg^-1·d^-1,坝地泥沙在埋藏条件下有机碳分解速率仅为被暴露在有氧条件下的11.4%,表明埋藏显著降低了有机碳分解速率。在缺氧条件下泥沙化学性质比有机碳分解相关微生物对泥沙有机碳分解速率的影响更大;在有氧条件下则表现为有机碳分解相关微生物对泥沙有机碳分解速率的影响更显著;泥沙物理性质对缺氧和有氧条件下泥沙有机碳分解速率的影响均较小。自然情况下,淤地坝表现为碳汇,但当发生溃坝时,原本在沉积缺氧条件下储存的泥沙有机碳会迅速暴露在空气中,有机碳分解速率显著提高,表现为碳源。     

Methanogenic community compositions in surface sediment of freshwater aquaculture ponds and the influencing factors

Aquaculture ponds represent ecologically relevant environments to study the community composition and diversity of methanogenic assemblages, as well as their interactions with cultivated species and chemical indicators. In this study, aquaculture ponds with crab (Eriocheir sinensis), oriental river prawn (Macrobrachium nipponense), perch (Micropterus salmonides) and Wuchang fish (Parabramis pekinensis) were sampled, and Illumina high-throughput sequencing was used to investigate the methanogenic communities. The results revealed that the abundant methanogenic orders in surface sediment were Methanomicrobiales, Methanosarcinales and Methanocellales. The relative abundance of Methanocellales was higher in crab and prawn ponds as compared to other ponds. Methanogenic 16S rRNA gene abundance and beta diversity of the community was affected by the cultivated species. Methanogenic communities in aquaculture ponds with higher contents of total nitrogen and organic matter had decreased species richness, while those with higher contents of ammonia and nitrite had an overall decreased abundance of methanogens and their respective diversities. Overall, in addition to the differences in cultivated species, the consequent differences in farming practices including the types and amounts of feeds used, the contents of total nitrogen, organic matter, ammonia and nitrite could all influence the methanogenic community in surface sediment of aquaculture ponds.     

三江源地区季节冻土时空格局及影响因子

根据三江源地区21个气象台站的最大冻土深度、气温、降水观测数据和欧洲中心再分析资料,利用旋转经验正交分解等方法对1981—1010年三江源地区季节最大冻土深度(MFSD)的时空分布特征进行了分析,并探讨了季节冻土与气候因子之间的关系,结果表明：(1)40年来三江源地区平均MFSD为136.66cm,空间分布呈现出以玛多站最大中心值(218.85cm),向四周递减的分布特征。(2) 40年平均变率空间分布和旋转正交经验分解第一模态时间系数均表现出三江源地区MFSD呈现明显下降趋势,季节冻土层明显减薄,平均MFSD递减率为0.51cm/a。(3)表征热力状况的气候因子中,湿润指数、气温和降水是影响三江源地区季节冻土较为重要的气候因子。(4)三江源地区季节冻土的关键区在东北部,MFSD典型高值年有1983年等4个年份;典型低值年有1988年等7个年份。通过对500hPa位势高度场典型高值年、低值年合成分析,季节冻土典型高(低)值年,北半球500hPa位势高度场负(正)异常;同时,南亚高压负(正)异常,其范围偏小(大),强度偏弱(强),温度场中心温度更低(高),对应三江源地区应季节冻土更厚(薄...     

机械作业下土壤理化性质和生态因子的变化

通过 3年对黄淮海农业机械化推广的研究 ,探讨了机械综合作业对旱作农业的影响 .结果表明 ,机械化秸秆还田、化肥深施、土壤深松和免耕覆盖等综合技术的合理配套实施 ,可以改善土壤理化性状 ,具有明显的生物学效应 .与传统作业相比 ,机械综合作业使土壤容重减少 0 .0 8g·cm-3 ,有机质含量增加12 % ,水分利用率提高 10 .1%～ 13.6 % ,小麦玉米产量增加 12 18kg·hm-2 .     

The role of chemical and physical factors in cancer development

The author deals with the effects of environmental chemical-, and physical carcinogens playing predominant role in nearly 90% of the cancer development. Different steps of chemical carcinogenesis, classification and evaluation of carcinogens according to the criteria of International Agency for Research on Cancer, and the most important biological markers of genotoxic exposures are presented. Among physical agents the carcinogenic effects of ionizing and nonionizing radiations are demonstrated, including limited, inadequate or proved carcinogenic action of UV, microwave, static and low-frequency electric and magnetic fields.     

Biological,chemical and physical characteristics of downwelling and upwelling zones in the hyporheic zone of a north-temperate stream

Along a single stream riffle, there is a typical flow pattern in which surface water enters the hyporheic zone in a downwelling zone at the head of the riffle and hyporheic water returns to the stream surface in an upwelling zone at the tail of the riffle. Distinct patterns of physical and chemical conditions in the hyporheic zone are likely to determine patterns of microbial activity and occurrence of hyporheic fauna. Interstitial water and core samples were taken at three depths in the downwelling and upwelling zones of a single riffle in the Speed River, Southern Ontario, Canada. Physical and chemical characteristics of the hyporheic water, bacterial density, protein content, detritus content and faunal composition of the hyporheic sediment were analysed. The downwelling and upwelling zones differed significantly in temperature, pH, redox potential, dissolved oxygen and nitrate with significant positive correlations occurring among the latter three. There were no differences in bacterial density or detritus content between the two zones nor between depths in either zone, but protein content, considered to be a measure of biofilm biomass, was significantly higher in the downwelling zone. Total density of hyporheic fauna and the number of taxa decreased with increasing depth in both upwelling and downwelling zones, and were positively correlated with surface water characteristics (oxygen, temperature and nitrate), sediment protein content and detritus; however, only a weak correlation was found with zone. The composition of taxa differed between the two zones, and faunal distribution was correlated with dissolved oxygen, detritus, protein content and depth.